The present invention relates to an integrated circuit device, an electronic instrument, and the like.
In recent years, a high-speed serial transfer such as low voltage differential signaling (LVDS) has attracted attention as an interface aiming at reducing EMI noise or the like. In such a high-speed serial transfer, data is transferred by causing a transmitter circuit to transmit serialized data using differential signals and causing a receiver circuit to differentially amplify the differential signals.
An ordinary portable telephone includes a first instrument section provided with buttons for inputting a telephone number and characters, a second instrument section provided with a liquid crystal display (LCD) and a camera device, and a connection section (e.g., hinge) which connects the first and second instrument sections. Therefore, the number of interconnects passing through the connection section can be reduced by transferring data between a first circuit board provided in the first instrument section and a second circuit board provided in the second instrument section by a high-speed serial transfer using small-amplitude differential signals.
A display driver (LCD driver) is known as an integrated circuit device which drives a display panel such as a liquid crystal panel. In order to realize a high-speed serial transfer between the first and second instrument sections, a high-speed interface circuit which transfers data through a serial bus must be incorporated in the display driver (see JP-A-2001-222249).
On the other hand, since the high-speed interface circuit handles differential signals with a small voltage amplitude of 0.1 to 1.0 V, for example, the high-speed interface circuit tends to be affected by noise from other signal lines. In particular, when noise from a signal with a large amplitude (e.g., scan signal transmitted through a scan line) is transmitted to the high-speed interface circuit, a malfunction such as a transfer error may occur.
A display panel includes an array substrate in which thin film transistors (TFTs) are disposed in an array, and a common substrate on which a common electrode is formed. The display driver outputs a data signal (source signal) supplied to the source of the TFT and a scan signal (gate signal) supplied to the gate of the TFT. The display driver generates and outputs a common voltage (common electrode voltage) applied to the common electrode.
In this case, the voltage difference between the voltage of the data signal and the common voltage is applied to a liquid crystal element. Therefore, when the common voltage generated by the display driver does not reach the desired voltage due to parasitic resistance and the like, the voltage applied to the liquid crystal element does not reach the desired voltage, whereby the display quality deteriorates.